The present invention relates to imaging flow. In particular, magnitude and directional flow information is provided.
In medical diagnostic ultrasound, power mode, color Doppler mode or spectral Doppler mode is used to detect flow information in a region being imaged. One or both of velocity and energy associated with the flow are estimated and used to display flow information. For example, color Doppler velocity detects both a direction of flow relative to the transducer (e.g., flow towards and flow away from the transducer) as well as the velocity or speed of the flow. For any single image, the color for spatial locations associated with flow is modulated as a function of the direction and magnitude of the velocity. For example, a red indicates flow towards a transducer and blue indicates flow away from the transducer, and the brightness of the blue or red color indicates the magnitude of the flow. Any single image presents the detected information to the user. However, the perception of flow through a sequence of images is negligible. For two- or three-dimensional imaging, the direction of flow being towards or away from the transducer provides even more limited directional information.
In an effort to provide further directional information, a two-dimensional directional vector is determined. For example, speckle is tracked from one frame of data to another frame of data. By determining a correlation in the speckle at translated positions between images, the two-dimensional direction of flow is determined. To communicate the flow information for a given image, a color wheel is used. Different colors are provided around the circumference of the wheel to represent flow in different directions. The magnitude or speed of the flow is calculated using the speckle correlation or angle corrected velocity information. Greater magnitudes are associated with brighter presentations of the color representing direction. Any single image presents the flow information to a user when displayed alone. However, the perception of flow through a sequence of images is negligible. The colors for subsequent images may or may not vary in brightness or hue from previous images, resulting in no perception of flow through a sequence of images. Due to the many colors in each image to depict the flow, the images are perceptually busy or disclose sufficient amounts of information that a user has trouble conceptualizing and using all of the information.